The present invention relates to a method and a system for configuring a monitoring device for monitoring a spatial area, in particular for configuring a monitoring device for failsafely monitoring a working area of a machine or installation, which is operated in an automated manner.
Working areas of machines or installations operating in automated manner are traditionally safeguarded by mechanical barriers (protective fences, protective doors) and/or by light barriers, light curtains, laser scanners et cetera as protection against accidents. As soon as a person or an object breaks through the barrier, the machine or installation is stopped or otherwise rendered harmless.
In the case of complex machines and installations, the expenditure for such protection can become very high. Light barriers, light curtains and the like must be aligned and mounted very accurately. Moreover, they can only monitor a straight area between light transmitter and light receiver so that a plurality of light barriers, light curtains et cetera are needed in order to protect a complex working area all around. In addition mechanical barriers and conventional light barriers, light curtains et cetera only provide limited flexibility so that the adaptation of the monitoring and protective spaces to changing working environments is expensive.
In order to avoid these disadvantages, it has been proposed for some time to safeguard the working spaces of hazardous machines and installations by means of cameras and modern methods of image processing. Such a method and a corresponding device are described, for example, in WO 2004/029502 A1, which is incorporated by reference herewith. This monitoring device uses at least two image recording units which simultaneously record the working area of the machine to be protected. The images of the two image recording units are subjected to stereo analysis including three-dimensional scenery analysis methods in order to determine range information.
DE 10 2004 020 998 A1, which is also incorporated by reference herewith, discloses another aspect of such a monitoring device, namely an advantageous implementation of the imaging optics for the image recording unit. In addition, it is proposed here to arrange at least one reference object within the monitored area in order to detect, for example, an impairment of the reliability of detection due to contamination, water drops and other items.
EP 1 065 522 B1 discloses a monitoring device wherein the propagation times of light pulses are detected by means of an image recording unit in order to obtain a three-dimensional image of a monitored spatial area. A comparison with previously stored reference values is supposed to allow to detect if an object has penetrated into a monitored area.
Further monitoring devices using image recording units are disclosed by DE 197 09 799 A1 and DE 101 38 960 A1. The first-mentioned document proposes a stereoscopic image evaluation for generating three-dimensional image signal sets and comparing them with corresponding reference signal sets. Objects can be detected if the current scene situation deviates from the reference model. DE 101 38 960 A1 proposes a method wherein range information is determined by means of brightness differences.
Finally, DE 41 13 992 A1 discloses a method for automatic three-dimensional monitoring of hazardous spaces wherein the images from at least two electronic imagers are evaluated with computer assistance in the monitoring phase. In this arrangement, the at least two imagers are calibrated to a common coordinates system This method operates in accordance with the principle of crossed light barriers. In the monitoring phase, the pixels of the imagers are checked for changes.
All these monitoring devices have in common that they attempt to record a three-dimensional image of the monitored spatial area in order to decide whether the machine or installation has to be stopped. The term “three-dimensional image” means an image of the spatial area which, in addition to the usual (2-dimensional) image, also comprises range information from individual or all objects in the spatial area. The range information can be obtained, for example, by propagation time measuring methods, stereoscopic image processing or in any other way.
Monitoring devices operating in accordance with this principle only need little installation and assembly expenditure since they can observe the spatial area from a central position. In addition, they are very flexible since the individual monitoring areas can be flexibly defined. In principle, arbitrarily curved courses and contours within the three-dimensional image can be defined as “virtual protection fences” or “virtual protection spaces”. As soon as an object penetrates into the virtual protection space or breaks through a virtual protection fence, a safety function is triggered as is known from the protection with protective doors, light barriers, light gratings and the like. It is also easily possible to change or adapt the virtual protection area when the machine or installation is in operation.
On the other hand, the high flexibility due to the virtual protection areas provides difficulties when setting up and configuring the monitoring device at a machine or installation. During assembly of a protective fence or a light curtain at a machine or installation, the course of the protection area can be easily recognized due to the mechanical arrangement of the barriers. However, this does not apply to the monitoring devices with virtual protection spaces.
Moreover, the position and the exact course of the virtual protection spaces is a safety-related feature. It should be ensured that a virtual protection space in reality extends exactly where it is intended to extend. Otherwise, undetected break-ins into the hazardous area of the monitored installation and thus grave injuries and personal damage could occur. In addition, it is desired to ensure that there are no gaps in the virtual protective fence which is difficult due to the high degree of freedom of design and flexibility of the virtual protective spaces.
Abovementioned DE 41 13 992 A1 proposes, for setting up a protective space, to place so-called measurement markings onto spatial positions which are intended to span a monitoring area. After that, the space coordinates of the measurement markings are determined by means of the recorded images. The space coordinates obtained span the monitoring area. However, this method for setting up monitoring areas is not optimal because the setting-up requires physical access to the marking points. In addition, DE 41 13 992 A1 does not disclose any mechanisms for ensuring failsafe configuration of a monitoring area.